1. Power control Considerations and framework for MS-MS Communications
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Eldad Zeira Voice:
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IEEE n at session #74 responding to call for comments for AWD issued after #73
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2. Power control Considerations and framework for MS-MS Communications Eldad Zeira, InterDigital

3. MS-MS communication needs to be power controlled
Massive resource reuse is a necessary condition to achieving high cell throughput
AWD recognizes this and allows HR-BS to schedule two or more MS-MS or MS-BS transmissions in same resources
Proper power control is essential in achieving spatial separation while maintaining each link quality

4. Design goals of power control procedures
Find power level that is close to the optimal as described above
Require little signaling overhead but retain HR-BS over-all control
Be easy to compute, especially by the forwarding HR-MS for which this is an extra burden
I.e. it is an addition to its own operation
Treat both repetitive and one-of transmissions, BUT
This paper treats power control for “repetitive” transmissions only
non-repetitive transmissions (e.g. ranging) out of scope for this contribution

5. System design affects choice of power control procedure
Resource allocation: centralized, distributed & hybrid
In “Hybrid” we use a combination of persistent and dynamic. This is baseline assumption in AWD.
Forwarding mode: “simple” or “cooperative”
Simple assumed in AWD.
Frame structure: location of MS-MS link (crosslink, or XL. MS-BS links are “traditional” links, or TRL)
UL only (other than e.g. some signals required for HR-MS discovery?)
DL only (no proposal for this case)
UL/DL, similar to ARS operation

6. Power control procedures: 802.16m
For data channels (incl. MAC messages)
SINRTarget is the target UL SINR needed at receiving MS
P is the TX power level (dBm) per stream and per subcarrier for the current transmission
L is the estimated average current DL propagation loss
NI is the estimated N+I at receiving MS.
Offset is a correction term.
SINRMIN(dB) is for minimum rate expected by ABS.
γIoT is the fairness and IoT control factor broadcasted.
SIRDL is the linear ratio of the downlink signal to interference power.
α depends on the number of receive antennas at receiving MS.
β is set to one to account for number of streams.
TNS is the total number of streams

7. Power control procedures: 2009 ([2] 8.4.10.3)
Closed loop PC
Open loop PC

8. Use cases and interference mechanisms for MS-MS: transmissions in UL only
In left of figure, MS (1) and (2) communicate on the XL while under BS control. In right of figure, MS (4) forwards data for MS (5). Both TRL (2)-BS and XL (1) – (2) interfere with TRL (3)-BS and XL (4)-(5). MS (5) transmitting on XL may or may not cause interference to other TRL but does interfere with XL

9. PC considerations for XL in UL: - Both HR-MS attached
DC or FTN
HR-BS controlled
Transmission to HR-BS:
Control by the HR-BS
Open or closed loops or both?
Use of Offset?
Control rate / measurements?
Proper use of baseline procedures (i.e or m-D12)
Transmission to another HR-MS
Control by HR-BS allows use of same procedures with receiving HR-MS reporting to HR-BS
As above, either use of Offset or m-like procedures can be utilized

10. PC considerations for XL in UL: - One HR-MS attached
DC or FTN
Forwarding HR-MS:
transmitting on TRL should be same as previous case
Transmitting on XL – power control done strictly from HR-BS would need much signaling (forwarded through same) – how to reduce overhead while retaining HR-BS control ?
Forwarded HR-MS may or may not be in a position to cause interference on TRL, but XL interference assumed.
Forwarded HR-MS receives power control commands from forwarding HR-MS.
Are these generated by HR-MS or by HR-BS (and forwarded)?
Do we want to create 2 procedures (w and without TRL interference)?
Reducing overhead while retaining HR-BS control

11. PC considerations for XL in UL: - No HR-MS attached
This case should be handled like the MS-BS link in baseline.
If a coordinator is used then it takes the role of the HR-BS in:
Controlling its own power using measurements and reports it may request from the non-coordinating HR-MS
Controlling the non-coordinating HR-MS as an HR-BS would

12. Interference mechanisms for MS-MS: transmissions in both UL and DL.
The following interference mechanisms exist:
interference of UL TRL to BS reception (normal cellular interference)
interference of UL TRL to XL TPSS to FPSS transmission
interference of UL XL (TPSS transmission) to BS reception on TRL
Interfere of DL XL (FPSS transmission) to MS reception on TRL
Interfere of DL XL (FPSS transmission) to MS reception on XL

13. PC considerations for XL in UL/DL:
Note slightly different interference mechanisms
TRL transmissions (to HR-BS) is always in UL, therefore same procedures can be applied.
Applies to the cases of single HR-MS and both HR-MS associated
Forwarded HR-MS power control
Same interfere mechanisms as for UL only therefore same procedures could apply
Also applies to the cases of single HR-MS and both HR-MS associated
Power control for forwarding HR-MS transmitting on XL in DL direction
This is really a new scenario, however -
May use identical procedure to that used for UL only (except for definition of resources for measurements etc.)

14. Text for 2009 based amendment
Power control for mobile to mobile communication Power control for two HR-MS associated with an HR-BS When two HR-MS that are associated with an HR-BS are transmitting to each other their power control related commands are generated by their serving HR-BS. The HR-BS may define measurements to be performed by the HR-MS on resources used for MS-MS communications and on the desired MS-MS signal to be reported to the HR-BS. Definition of power control procedure is TBD.

15. Text for 2009 based amendment - cont’d
Power control for one HR-MS associated with an HR-BS The transmission power of a forwarding HR-MS transmitting to forwarded HR-MS is controlled by messages from the forwarded HR-MS that are derived from HR-BS controls The transmission power of a forwarded HR-MS is controlled by messages from the forwarding HR-MS that are derived from HR-BS controls Power control procedure details TBD

16. Text for 2009 based amendment - cont’d
Power control for no HR-MS associated with an HR-BS
If a coordinator is used then it controls transmission power for the pair in the same way as a baseline HR-BS would.

17. Text for 802.16m based amendment
Power control for mobile to mobile communication Power control for two HR-MS associated with an HR-BS When two HR-MS that are associated with an HR-BS are transmitting to each other their power control related commands are generated by their serving HR-BS. The HR-BS may define measurements to be performed by the HR-MS on resources used for MS-MS communications and on the desired MS-MS signal to be reported to the HR-BS. Definition of power control procedure is TBD

18. Text for 802.16m based amendment- cont’d
Power control for one HR-MS associated with an HR-BS The transmission power of a forwarding HR-MS transmitting to forwarded HR-MS is controlled by messages from the forwarded HR-MS that are derived from HR-BS controls The transmission power of a forwarded HR-MS is controlled by messages from the forwarding HR-MS that are derived from HR-BS controls Power control procedure details TBD

19. Text for 802.16m based amendment- cont’d
Power control for no HR-MS associated with an HR-BS If a coordinator is used then it controls transmission power for the pair in the same way as a baseline HR-BS would.

20. References
[1] m amendment (D12)
[2] “2009”
[3] UL open loop PC recommendations IEEE s802.16m-09/0546